1. Field of the Invention
The present invention generally relates to a portable terminal. More particularly, the present invention relates to a portable terminal having an antenna device that can offer an appropriate transmission/reception performance according to a propagation environment.
2. Description of the Related Art
Typically, a portable terminal is a device that provides a wireless communication function between users or between a user and a service provider through a mobile communication Base Station (BS). A variety of contents including voice calls, short message transmission, mobile banking, Television (TV) broadcasting, on-line gaming, Video On Demand (VOD), etc., are provided to users through their portable terminals.
According to their outward appearances, portable terminals are categorized into a bar type, a flip type, and a folder type. The bar-type terminal has a communication circuit and an input/output device, such as a transmitter and a receiver, in a single housing. The flip-type terminal further includes a flip cover secured onto a bar-type terminal. The folder-type terminal is characterized by a pair of housings engaged with each other rotatably and input/output devices distributed to the housings. Along with the recent emergence of a sliding-type terminal, efforts have been made to satisfy diverse tastes of users, increasing portability and user-friendliness, with the sliding-type terminal together with the folder-type terminal.
Also, mobile communication services are diversifying, and how include on-line gaming, transmission of moving picture files, mobile banking, VOD, Digital Multimedia Broadcasting (DMB), etc., through portable terminals. The diversification of mobile communication services is attributed to the proliferation of portable terminals and various user demands that are a driving force behind commercialized provision of various contents through portable terminals.
Various types of antenna devices are installed in portable terminals to provide various services. Since all areas are not under a good and uniform propagation environment in real implementation, the antenna devices are typically designed in such a manner that users select appropriate antennas according to their propagation environments. That is, even though a user does not select a particular antenna device in a good propagation environment, his terminal is capable of transmission and reception. In a bad propagation environment, the user may additionally install an antenna module to the portable terminal or pull out an external antenna of the portable terminal.
A problem encountered with installing antenna devices is that transmission/reception signals interfere with each other between different antenna devices. For example, a terminal with an internal antenna and a retractable external antenna can ensure a sufficient transmission/reception performance with the internal antenna alone in a good propagation environment, whereas the external antenna is extended in a bad propagation environment. With the external antenna inserted, a noise signal is introduced to the external antenna, resulting in degradation of signal quality. That is, when only the internal antenna operates, a noise signal is introduced to the external antenna and thus the internal antenna does not perform optimally. Similarly, when the external antenna is extended, a noise signal introduced to the internal antenna prevents performance unique to the external antenna.